In the motor-vehicle sector frequently filaments of metal are applied onto windscreens in order to ensure rapid defrosting in climatic conditions such as rain, snow or ice.
Generally, during the process for manufacturing windscreens, as in the manufacture of safety glass, it is envisaged bonding together two glass planes by means of a sheet of polyvinyl butyral (PVB).
In particular, during the manufacture of windscreens which incorporate conductive filaments, these filaments are applied onto the sheet of polyvinyl butyral before it becomes an integral part of the windscreen itself.
Usually the metal filaments positioned along straight paths parallel to each other are laterally confined by conductive strips, so-called “busbars”, which are configured to distribute electric current in each of the filaments so as to ensure operation thereof.
In this sector, the operations of applying the busbars, are usually performed manually by an operator, with the metal strip usually being applied by means of a hot iron.
The manual operation performed by the operator is necessary to ensure the working accuracy and precision required during positioning of the element to be fixed onto the plastic support, in particular when applied along curved paths.
The main disadvantage of the manual system used in the prior art is that such manual application results in extremely high manufacturing costs both in terms of manufacturing time and in terms of labour.
A further disadvantage is the lack of reproducibility of the quality of the end product, a characteristic which is mainly dependent on the experience and skill of the operator who performed the application operation.
In particular, in operations involving the application of conductive elements onto plastic supports, insufficient heating of the joining zone may result in incomplete application of the element onto the support. Similarly, excessive heating may result in local deterioration of the plastic support with a consequent weakly set joint during cooling of the working zone.
Therefore, inadequate heating of the joining zone between conductive element and support surface gives rise, during quality control checks, to a large number of rejects.